Fix mozilla-services#3532, remove .nsprc file now that tough-cookie h…

…as been updated

As seen in [1], we had to temporarily disable nsp checks due to a
potential vulnerability in tough-cookie. The request library has been
updated to use the updated tough-cookie, and, thanks to loose version
tracking, looks like the fix percolates up to all our deps.

[1] https://circleci.com/gh/mozilla-services/screenshots/3561